212778021 has 4 divisors (see below), whose sum is σ = 283704032. Its totient is φ = 141852012.

The previous prime is 212777993. The next prime is 212778023. The reversal of 212778021 is 120877212.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 212778021 - 2¹⁹ = 212253733 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 212778021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (212778023) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 35463001 + ... + 35463006.

It is an arithmetic number, because the mean of its divisors is an integer number (70926008).

Almost surely, 2^212778021 is an apocalyptic number.

It is an amenable number.

212778021 is a deficient number, since it is larger than the sum of its proper divisors (70926011).

212778021 is an equidigital number, since it uses as much as digits as its factorization.

212778021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70926010.

The product of its (nonzero) digits is 3136, while the sum is 30.

The square root of 212778021 is about 14586.9126616978. The cubic root of 212778021 is about 597.0017283464.

The spelling of 212778021 in words is "two hundred twelve million, seven hundred seventy-eight thousand, twenty-one".